The Toyota 8" axle makes use of a dropout differential, or third
member). Because of this, a drain plug is installing on the bottom of
the axle housing to allow for draining the gear oil. Other types of
axles feature a cover plate that serves this same purpose. One problem
with the low hanging drain plug is that it is prone to getting hung up
on rocks, and it can also become damaged to the point where removal is
difficult, or worse yet can get knocked loose causing the loss of the
gear oil in the axle. Several improvements on the drain plug have
included low profile socket plugs, to welded in place plugs with
alternate method of oil draining.

A second problem with the axle housing is that while the steel in the
main part of the housing is approx. 3/16" thick, the steel in the
face of the housing is perhaps 1/16" thick. It is susceptable to
damage from contact with rocks and if pushed in far enough, it can
contact the ring gear, either damaging the gear or letting the gear cut
through the steel and create an oil leak. There are several forms of
"diff armor" on the market to address this issue.

Over the years, I've tried a number of these techniques to beef up the
axle to withstand trail abuse. Each problem could be addressed
individually to some degree, but I wanted something cleaner and that
would address all the issues at once. Below, is a rear Toyota axle
housing showing the bottom section, containing the drain plug, cut out
and replaced with a flat bottom plate that also wraps around the front
(or rear) of the housing:

I developed an easy to install kit, pictured below, that incorporates a
flat replacement for the bottom of the axle housing and a curved
protector for the face of the housing, all out of 1/4" thick steel:

Remove the differential and clean the inside of the housing of gear oil

Mark the outline of the cutout area, using the included template (B)

Remove the lower four studs, the two lowest ones will become the oil
drains (C)

Make straight line cuts are made to remove the bottom of the housing:
(C)

Cutoff wheel, sawzall, oxy-acetylene cutting torch or plasma cutter
will make the cut

The opening is ground out to allow the plate to drop in (D)

You can cut/grind the back egde of the rear axle housing to let the
plate sit in deeper if you have the rear pinion tipped up for a CV
shaft

And with the non-diff. protetor plate, the plate just sits on the front
and rear flange and does not extend past the front flange.

Weld the plate in place, first tacking the corners then weld in short
sections, allowing the housing to cool in between (E)

Filling the bottom (actually the top) of the housing with water helps
soak up the heat

For the diff. protector plate, bend over the three tabs and add the
protector plate around the housing and weld in place

If needed, grind a deeper groove where the tab bends over the housing
or heat to make it easier to bend

Fill in the groove after bending.

The two small steel wedges can be used to fill the gaps on the ends
where the tabs meet the housing

The inner seams can also be welded closed for a stonger and more
leakproof installation

Grind the outside welds smooth, clean, prime and paint as desired (F)

Tip the housing back and fill it with water or paint thinner to check
for leaks

If a leak is detected, re-weld the inside or outside as needed

Clean the inside of the housing and if desired, apply an oil proof
primer/paint, such as POR-15

To replace the oil drain plug the two existing lower studs that hold
the 3rd member in place are converted to bolts by welding the nuts to
the stud after its tight

These parts are not included in the kit, you re-use your old studs and
nuts

Alternately, you can use some M8-1.25 bolts for the lower two studs in
place of welding the nut to the stud

We can supply the proper sized grade 10.9 metric bolts and lock nuts
for the stud upgrade, enquire
for details.

You may find that it is easier to install the 3rd member if you drill
out the mounting holes a little oversize

Use a bit about 1/64"to 1/32" larger than the existing hole
to clean it up and make it easier to slip over the studs

Re-install the axle on the vehicle

The end result of a couple of hours work is an axle that has 3/4"
- 1" additional ground clearance (equivalent to a ~2" tire
size increase), a smooth base to easily slide over trail obstacles, an
integral diff protector and no drain plug to get damaged or lost.